5-6-guess.c

#include <stdio.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <fcntl.h>
#include <unistd.h>
#include "tlpi_hdr.h"

int main(int argc, char *argv[])
{
    int fd1;
    int fd2;
    int fd3;
    char * file = argv[1];

    fd1 = open(file, O_RDWR | O_CREAT | O_TRUNC, S_IRUSR | S_IWUSR);
    fd2 = dup(fd1);
    fd3 = open(file, O_RDWR);
    write(fd1, "Hello,", 6);
    write(fd2, "world", 6);
    lseek(fd2, 0, SEEK_SET);
    write(fd1, "HELLO,", 6);
    write(fd3, "Gidday", 6);
}